Production of patterned paper

Abstract

Speckle-patterned paper is produced on the paper machine without the use of printing techniques by first preparing speckle-forming material and then introducing this into a contrasting color papermaking furnish. Paper is then made from the speckle-containing furnish in the normal way. The speckle-forming material is produced either by agglomerating a mixture of papermaking fiber, particulate pigment and, preferably, a latex or other binder or by dry comminution of cellulose fiber aggregates in the form of paper or entangled fiber clumps.

What is claimed is: 
     
       1. A process for the production of patterned paper, said process comprising the steps of: (1) preparing speckle-forming material by either: (A) agglomerating a mixture comprising papermaking fibre, particulate pigment, and a latex or other binder in an amount of up to about 20% by weight, based on the weight of dry latex or other binder to weight of dry fibre in the speckle-forming mixture, by the addition to the mixture of at least one polyelectrolyte flocculant, polyelectrolyte coagulant or other polyelectrolyte agglomerating agent; or   (B) dry comminution of cellulose fibre aggregates;     (2) introducing the resulting speckle-forming material into a papermaking furnish having fibres of a contrasting colour to the colour of the speckle-forming material and in which dye, if present, has been fully fixed; and   (3) draining the speckle-containing furnish to produce a patterned paper web.   
     
     
       2. A process as claimed in claim 1, wherein the speckle-forming material is prepared by (A) agglomerating a mixture comprising papermaking fibre, particulate pigment, and a latex or other binder in an amount of up to about 20% by weight, based on the weight of dry latex or other binder to weight of dry fibre in the speckle-forming mixture, by the addition to the mixture of at least one polyelectrolyte flocculant, polyelectrolyte coagulant or other polyelectrolyte agglomerating agent. 
     
     
       3. A process as claimed in claim 2, wherein a combination of oppositely-charged polyelectrolyte agglomerating agents are used to agglomerate said mixture. 
     
     
       4. A process as claimed in claim 3, wherein anionic polyelectrolyte flocculant polyelectrolyte and cationic flocculant or coagulant are each added in an amount of from 0.2% to 1.0% by weight, based on the dry weight of fibres in the speckle-forming mixture. 
     
     
       5. A process as claimed in claim 3, wherein anionic polyelectrolyte flocculant and cationic polyelectrolyte flocculant or polyelectrolyte coagulant are each added in aqueous solutions of concentration 0.5% to 0.75% by weight. 
     
     
       6. A process as claimed in claim 3, wherein the speckle-forming material is produced by adding anionic polyelectrolyte flocculant to an aqueous mixed suspension comprising papermaking fibre, pigment, and latex or other binder, and subsequently adding a cationic polyelectrolyte flocculant or polyelectrolyte coagulant. 
     
     
       7. A process as claimed in claim 6, wherein the papermaking fibre content of the aqueous suspension prior to the anionic flocculant addition is from 1.5% to 3% by weight. 
     
     
       8. A process as claimed in claim 2, wherein the latex is a styrene-acrylic or styrene-butadiene latex. 
     
     
       9. A process as claimed in claim 2, wherein the papermaking fibre in the speckle-forming mixture is a blend of hardwood and softwood fibre, of which softwood constitutes at least 30% of the total weight of fibre in the blend. 
     
     
       10. A process as claimed in claim 2, wherein the pigment in the speckle-forming mixture is titanium dioxide. 
     
     
       11. A process as claimed in claim 2, wherein agglomerated speckle-forming material is introduced into the papermaking furnish at a level of about 10% to 20%, based on dry weight of speckles to dry weight of fibre and filler in the papermaking furnish. 
     
     
       12. A process as claimed in claim 1, wherein the speckle-forming material is prepared by (B) dry comminution of cellulose fibre aggregates. 
     
     
       13. A process as claimed in claim 12, wherein the cellulose fibre aggregates are in the form of fibre clumps. 
     
     
       14. A process as claimed in claim 13, wherein the fibre clumps comprise hemp fibres. 
     
     
       15. A process as claimed in claim 12, wherein the cellulose fibre aggregates subjected to dry comminution are in the form of paper. 
     
     
       16. A process as claimed in claim 15, wherein the dry-comminuted speckle-forming material is added to the papermaking furnish at a level of about 5 to 15%, based on dry weight of speckles to dry weight of fibre and filler in the papermaking furnish. 
     
     
       17. A process as claimed in claim 15, wherein the dry-comminuted speckle-forming material is added to the papermaking furnish in the form of an about 1.5% to 3% aqueous suspension.